My new thinwall aluminum M6 spacer for the generator light on the Nitto M12 rack deformed under torque, and wouldn’t hold the light firmly enough.
I replaced it with a section of stainless tubing. It has a 5/16″ ID, so a 6mm (M6) bolt slides right through. Officially, the tube was marked Stock No. 7117, Stainless Tube, 5/16 x .028. You can probably scan the barcode right off the photo.
I also got a tube cutter, since I can’t find my small red one. This is a bigger one, since the other one may turn up, and the adjustment knob is easier to turn. It’s big enough to cut all the seatposts in the house, except the one I actually want to cut.